The present invention relates to methods of determining the quantitative content of gaseous or vaporous impurity in a gas mixture and to devices for accomplishing said methods.
The present invention can be used most effectively for studying the composition and properties of substances in chemistry and petroleum chemistry as it provides fire and explosive safety and high corrosion resistance in aggressive mediums.
Known in the art are methods of determining the quantitative content of gaseous or vaporous impurity in a gas mixture, based on the agitation of a laminar jet upon the emergence of the impurity being determined. For example, in order to determine the quantitative content of impurity in a gas mixture, the latter is formed into a jet after which the total head of said jet is recorded.
However, said method is not sensitive enough to variations in the quantitative content of impurity in a gas mixture.
Known in the art are methods of determining the quantitative content of gaseous or vaporous impurity in a binary gas mixture, based on measuring the total head whose value depends on aerodynamic friction losses upon laminar flow of gas jet. Such a method is used for measurements when no high sensitivity is required, for example, in the synthesis of ammonia, at a hydrogen content in nitrogen of from 50 to 80 percent by volume. Some methods are based on variations in the jet head losses upon transition from laminar to turbulent flow. Such methods are utilized in instruments designed to meet higher sensitivity requirements, for example, in indicators of the presence of oil vapors in the air in a concentration of from 0.3 to 0.5 percent by volume.
U.S.S.R. Inventor's Certificate No. 332,453 discloses a pneumatic indicator comprising: channels for the delivery of a gas being analyzed and reference gas; a sensing element comprising a feed capillary and an inlet tube, both arranged coaxially in a common housing, the inner space of the housing being coupled with a suction device; a comparison element, one of whose inputs is coupled with the sensing element output; an oscillator; a "throttle-receptacle" link; a power amplifier and an output channel. Said indicator differs from other prior art in that it comprises switches at the sensing element input and at the comparison element output, the two inputs of the first one of said switches being connected with the channels for the delivery of the gas being analyzed and of reference gas, respectively, while the first output of the second switch is connected via power amplifier to the indicator output channel and the second output is connected via "throttle-receptacle" link to the comparison element input, the receptacle in said latter link containing a dividing diaphragm whose control space is coupled with the oscillator output connected, in turn, to the control inputs of both switches.
Said pneumatic indicator comprises, as seen from the aforecited claim, a large number of elements, which tends to complicate the instrument and affect its reliability. Such devices are noted for their complicated circuits designed primarily to maintain the working parameters of the sensing elements upon variation of ambient temperature or of feed air pressure.
U.S.S.R. Inventor's Certificate No. 395,723 discloses a pneumatic gas analyzer-and-indicator comprising a fluid-jet sensing element whose input is coulped via first switch with channels for gas being analyzed and for reference gas, an ejector whose input is coupled to the sensing element chamber, a comparison element whose one input is connected to the sensing element output, and a timing pulse generator connected with two switches. Said prior art device is distinguished in that it is provided with a damping link and a throttle divider whose input is coupled with the ejector input while the output is connected with the second input of the comparison element whose output is connected via second switch to an output channel of the device and, via damping link, to the ejector control channel.
Said pneumatic gas analyzer-and-indicator is structurally simpler than that disclosed in U.S.S.R. Inventor's Certificate No. 332,453, however, its sensitivity to impurities being analyzed is much lower.
Most of the prior art instruments are characterized by complicated circuitry involving a large number of diaphragm elements which affect considerably the reliability of the instrument operation and complicate their manufacture and repair.
An intensive development of chemical industry places stricter requirements upon the sensitivity of methods and means of measuring impurities in gas mixtures.
For example, the presence of moisture in processes involving chlorine-containing materials results in premature corrosion of the equipment, decomposition of catalysts and deterioration of the quality of produce.
Neither prior art methods based on the laminar flow of a gas mixture jet, nor those based on the transition from laminar to turbulent flow, can meet modern technological requirements.
Similar difficulties are encountered when using prior art instruments for accomplishing the afore-listed methods.
The absence of structurally simple and reliable devices for realization above-mentioned methods makes it rather difficult to determine impurities in gas mixtures.